Grate bar for sintering machine



May 20, 1958 F. c. WOODY 2,835,485.

GRATE BAR FOR SINTERING MAHINE Filed Dec. 15, 1955 2 Sheets-Sheet 1 May20, 1958 F. c. WOODY GRATE BAR FOR SINTERING MACHINE 2 Sheets-SheetFiled Dec. 15, 1955 \NN \NNI INVENTOR.

FPEQ c. Waaa BY ATTO/P/I/[V United States Patent GRATE BAR FUR SENTERINGMAQHINE Fred C. Woody, Garfield Heights, Ohio, assignor to NationalMalleable and Steel (Tastings Company, Cleveland, @hio, a corporation of@ln'o Application December 15, 1955, Serial No. 553,323

7 Claims. (Cl. 266-41) This invention relates to sintering machines, andmore particularly to a finger type grate bar therefor.

In sintering machines of the usual type there is an endless conveyormade up of a series of pallets on which grate bars are mounted. Duringoperation of the machine, the conveyor carries the pallets to thedischarge end where the pallets travel downwardly and the sinteredmaterial resting on top of the grate bed is discharged. The pallets thentravel along a lower track back to the feeding end where they are liftedup by the conveyor to the upper level again to repeat the process.During the aforementioned travel along the lower track of the conveyor,the pallets are in an upside-down position. With the pallets in thelatter position, some means must be provided to maintain the grate barsin assembled relationship with the pallets.

In United States Patent No. 2,322,873, issued June 29, 1943, to WilsonH. Moriarty, there is shown a finger type grate bar construction inwhich each bar has a pair of downwardly extending retaining lugs on theunderside thereof. These lugs are disposed near the central portion ofthe bar, and are adapted to underlie centrally disposed stops on thepallets. Accordingly, as the pallets drop to upside-down position, thelugs on the grate bars engage the stops on the pallets, thus preventingthe bars from falling out of assembled relationship with the pallets.

It has been found that in service the outer ends of the type of gratebar shown in the aforementioned patent have a tendency to warp upwardly,probably due to the repeated heating and cooling of the bars duringsintering operations. This warpage of the bars is undesirable forvarious reasons, one being the resulting uneven surface of the gratebed. in addition, the warped outer ends of the bars sometimes become sopositioned that they overlap adiacent bars, thus leaving gaps in thegrate bed adjacent its outer edges. The lateral edges of the grate barsadjacent these gaps burn out and deteriorate much faster than theremaining portions of the bars, due to the increased passage of hotgases through these openings and also due to the abrasive wear caused bythe sintered material dropping down through these gaps. Consequently,the bars do not wear uniformly throughout their full length and have tobe replaced prematurely. Moreover, the material dropping down throughthe gaps in the grate is lost during the sintering process and createsan untidy state in the area surrounding the sintering machine.Furthermore, the sintered material lost from the grate causes increasedwear on the circulating fan and duct system.

It is, therefore, a general object of the invention to provide a novelgrate bar construction in which the bars do not warp in service.

Another object of the invention is to provide a grate bar in which theouter ends thereof will remain in a substantially horizontal positionregardless of the length of time the bar is used in service.

A further object of the invention is to provide a finger type grate barand associated pallet construction for a sintering machine, in whichmeans is provided on the bar to eliminate the tendency of the outer endsof the bars to warp vertically away from the top surfaces of the pallet;

A more specific object of the invention is to provide a rate bar havinga plurality of spaced anti-Warping ribs extending downwardly from itsunderside throughout substantially the entire longitudinal extent of thebar.

A still further object of the invention is to provide a finger typegrate bar having anti-warping ribs thereon and adapted for use with apallet construction, for a sintering machine, comprising a plurality ofspaced transversely extending supporting portions.

Other objects and advantages of the invention will be apparent from thefollowing description taken in conjunction with the drawings, in which:

Fig. 1 is a diagrammatic view of a sintering machine, showing the pathof travel of the pallets therein.

Fig. 2 is an enlarged plan view of one of the pallets shown in Fig. 1,with a plurality of grate bars embodying the invention mounted thereon.

Fig. 3 is a vertical sectional view, taken generally on line 3-43 ofFig. 2, one of the transverse supporting walls of the pallet beingremoved to better illustrate the structure of the grate bar.

Fig. 4 is a vertical sectional view taken on line 44 of Fig. 2.

Fig. 5 is an enlarged end elevational view taken from the right of thegrate bar shown in Fig. 4.

Fig. 6 is an enlarged vertical sectional View taken along line 6-6 ofFig. 4.

Fig. 7 is an enlarged horizontal sectional view taken along line 7--'7of Fig. 4.

Fig. 8 is reduced scale vertical sectional view similar to Fig. 4 butshowing a modification of the invention.

Fig. 9 is a reduced scale side elevational view of an existing grate barshowing the warpage that has been found to occur in service.

Referring to the drawings, there is shown the invention applied to asintering machine of the usual type, but it will be understood that itmay be applied to any machine in which sintering or like operations arecarried on. The sintering machine comprises a series of pallets 10mounted on an endless conveyor, as shown in Fig. l. The pallets 10receive and discharge the material to be sintered. At the discharge endA of the machine, the pallets drop to an upside-down position and travelthus until the loading end B is reached, at which time they are raisedto upright position.

Pallet it: comprises a generally rectangular frame 11 which extendstransversely of the sintering machine. Frame 11, as shown in Figs 2 to4, inclusive, comprises longitudinally extending spaced members or sidewalls 12 and 14 connected by transversely extending forward and rearwardmembers or walls id16 and intermediate members or walls lid-18.Extending upwardly from walls 12 and i4 and integral therewith areportions 17 for confining the material being sintered. Each of walls 12and 14 is provided with depending brackets 20 which may be reinforcedupon the pallet frame by means of webs 22. Brackets 20 are adapted toreceive means for moving the pallet upon the track of the sinteringmachine.

Mounted on pallet frame 11 for supporting the material to be 'sinteredare a plurality of finger type gratebars comprising end bars 26 andintermediate bars 28. Each bar comprises an elongate body portionadapted to extend across the supporting members or Walls 16 and 18 ofthe pallet and rests thereon by engagement of correspondingly spacedunder-surfaces of the body portion with the body or walls, as shown inFigs. 4 and 8. The bars are positioned to extend in the directionoftravel of the pallet, thus permitting the use of a shorter bar andproviding a more flexible grate for the sintering process. In theembodiment shown, spacing projections 30 are provided on both sides ofbars 28 so that when the bars are assembled on the pallet, openings 32are formed which permit the passage of air and hot' gases through thecharge during sintering. It will be understood, of course, thatprojections 39 may be formed on only one side of body portions of thebars instead of both sides, as illustrated.

The underside of each of bars 28 is formed with a pair of downwardlyextending retaining lugs 34 and 35 disposed near the central portionthereof. These lugs are spaced'from and underlie transversely extendingstops 36' on intermediate walls 18 of the pallet frame and allow thebars to drop away from the pallet a predetermined amount when the latteris in the aforementioned upsidedown position. Stops 36 may be eithersecured to walls 18 or formed integrally therewith.

It will be observed that retaining lug 34 is spaced closer to'theunderside of the opposing stop 36 than is lug 35. With this zurangementof the lugs and stops,

when the pallet drops to upside-down position in the operation of thesintering machine, lug 34 will be the first to engage the opposing stop36 on wall 18 of the pallet-and arocking action of the bar will tend tooccur.

The extent of rocking is limited by the subsequent engagement of lug 35on the bar with its opposing stop on the pallet. This rocking of thegrate surface during the discharge operation acts to effectively loosenthe sintered material to permit it to drop away from the grate and.thus-maintain the air passages 32 clear.

In accordance'with the invention, the underside of each of bars 28 isformed with a plurality of spaced, antiwarping means 38 extendingdownwardly from the elongated body portion of the bar. Means 38comprises depending ribs or projections 40 disposed near the outer endsof the bar and rib 42 disposed at the central portion of the bar betweenretaining lugs 34 and 35. Outer ribs 40 in the embodiment shown have ageneral configurations in vertical cross-section of an invertedisosceles triangle, having its vertex rounded or arcuate in shape, asindicated at 44 (Fig. The side surfaces 46 of ribs 40 merge with andform plane continuations of the tapered side surfaces 48 of the gratebar proper. The ends of the ribs are also of roundedcontour and divergeupwardly to merge with the underside of the grate bar.

Central rib 42 extends between retaining lugs 34 and 35 on the undersideof the bar and as best seen in Fig. 7, the sides 50 of the rib convergetoward the vertical axis of the grate bar. In a vertical direction,sides 50 diverge upwardly and merge with sides 48 of the grate barproper.

It has been found that the vertical dimension of strengthening ribs 40and 42 should be at least as great as, and preferably a little greater,than the vertical dimension of the body portion of the grate bar proper.The reason for this relationship is that the ribs 40 and 42, asdescribed, represent a substantial portion of the metal of the grate barand as the bars are repeatedly heated and cooled during a continuoussintering process, ribs 40 and 42, being disposed well below the heatingor sintering zone of the grate bed, are not subjected in any greatdegree to this constant variation in temperature. Furthermore, becauseof the downward convergence of the sides of the ribs, they are lesssubject to the effect of the hot air and gases passing through openings32 in the grate bed. In addition, the convergence of the ends of outerribs 40 likewise aids in eliminating the effect of the down draft andthus helps to maintain the ribs at a lower operating temperature.

It will be seen that the junctures of the ends of ribs 40 with theunderside of the bar are disposed as close as practicably possible tothe supporting walls 16 and 18 of the pallet to thus position asubstantial portion of the metal of the grate bar below the heating zoneof the grate bed. It will also be apparent that outer ribs 40 add to theproportionate weight of the outer ends of the bars, thereby tending tomaintain the latter in engagement with the top surfaces of support walls16 of the pallet when the latter is in upright position.

During the sintering process and consequent repeated heating and coolingof the bars, the ribs 40 and 42 will prohibit or substantially limitwarping of the bars, as so frequently occurs in conventional finger typegrate bars (Fig. 9). Thus, by preventing or limiting warpage, asubstantially even grate surface is maintained and the bars tend to wearuniformly throughout their entire length. It will be understoodtherefore that the invention provides a longer wearing and moreeconomical grate.

It will be apparent to those skilled in the art that the design of ribs40 and 42 lends itself to the economical production of molds for castingthe grate bars especially as concerns the drawing of the patterns duringthe molding process.

Retaining lugs 34 and 35 and ribs 40 on the bars are spaced from walls16 and 18 on the pallet, as at 49 (Fig. 4) to provide for horizontalmovement of the bars with respect to the pallet, or in a directionlongitudinally of the bars. This movement additionally aids in breakingup the sintered material during discharge to maintain the air passages32 clear. I

In assembling bars 28 on the pallet, each bar is lowered into space Cadjacent the side of either wall 12 or 14 with retaining lugs 34, 35 andassociated strengthening rib 42 between transverse walls 18 and outerstrengthening ribs 40 between transverse walls 16. As the ends of stops36 do not extend to side walls 12 and 14 of the pallet, there is nointerference between lugs 34 and 35 and the stops in this position ofthe bar. The bar may then be moved transversely to the center of thepallet and the rest of bars 28 assembled in a like manner. The grateassembly is completed by adding one of bars 26 to each end of thepallet, as shown in Figs. 2 and 3, and inserting pins 50 throughopenings in side walls 12 and 14. It will be observed that a limitedamount of vertical movement of end bars 26 with respect to the pallet ispermitted by the looseness of the fit of pins 50 in the pallet. Relativemovement of end bars 26 in a lengthwise direction is limited bydepending projections 52 (Fig. 3) which are adapted to engage walls 1616on the pallet frame.

An important aspect of the novel grate bar is that it may be used withexisting conventional pallets of the type comprising spaced transverselyextending support walls, thus facilitating interchangeability of the barwith those used in present sintering machines.

In Fig. 8 there is shown a modification of the invention in which theretaining lugs 54 project inwardly toward the transverse center line ofthe bar instead of outwardly, as in the previous embodiment. In thisconnection the pallet frame of the modification comprises a singleintermediate wall 56 with transverse stop means formed on both sides ofthe wall. The modified bar does not have a central strengthening rib asin the previous embodiment and outer anti-warping ribs 58 merge withretaining lugs 54 to form a unitary structure. The remainder of the barand the pallet construction is similar to the first de scribedembodiment, and operation and assembly is practically identicaltherewith.

From the foregoing description and accompanying drawings, it will bereadily understood that a novel finger type grate bar for a sinteringmachine or like device is provided comprising means on the underside ofthe bar which eliminates warping of the bar upwardly, away from thesupporting surfaces of the pallet to thus provide a much longer wearingand more economical grate.

The terms and expressions which have been employed are used as terms ofdescription and not of limitation and there is no intention, in the useof such terms and expressions, of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention claimed.

What is claimed is:

1. In a grate assembly, a pallet comprising a plurality of spacedsupporting members, a grate bar having an elongate body portion adaptedto extend across said supporting members and rest thereon by engagementof correspondingly spaced undersurfaces of said body portion with saidmembers, said grate bar having longitudinally extending anti-warpingribs integral with the body portion and separated by said undersurfaces,said ribs projecting downwardly free of the members from the level ofthe undersurfaces for a distance substantially equal to the depth of thebody portion to dispose the ribs below a work-heating zone of the grateassembly whereby they are maintained in a cooler and stronger state thansaid body portion.

2. The grate assembly of claim 1 wherein opposite side surfaces of theribs extend away from said body portion in converging directions.

3. The grate assembly of claim 1 wherein opposite side surfaces andopposite end surfaces of the ribs extend away from said body portion inconverging directions.

4. The grate assembly of claim 1 comprising downwardly-facing abutmentmeans carried on certain of said members, and lugs positioned on certainof said ribs to extend underneath the abutment means in the normalupright position of said assembly, and the ribs have a depth at leastequal to that of the body portion.

5. In a sintering machine having a heating or sintering zone, an endlessconveyor extending thereunder comprising an upper track and a lowertrack, a pallet adapted to be carried by the conveyor along both tracksand comprising spaced parallel supporting members, abutment meanscarried on certain of said members, a grate bar having an elongate bodyportion adapted to extend across said supporting members and restthereon by engagement of correspondingly spaced undersurfaces of saidbody portion with said members, said grate bar having anti-Warping ribsintegral with the body portion and separated by said undersurfaces, inthe upright position of said pallet along the upper track, said ribsprojecting downwardly free of the members from the level of theundersurfaces for a distance substantially equal to the depth of thebody portion to dispose the ribs sufficiently away from the top surfaceof the bar whereby the ribs are maintained in a cooler and strongerstate than said body portion, the grate bar at said position of thepallet having lugs extending underneath the abutment means for supportof the bar when the pallet is positioned upsidedown along the lowertrack.

6. The sintering machine of claim 5 wherein said lugs project from endportions of said ribs.

7. A grate bar for use on a pallet of a conveyor-type sintering machinecomprising an elongate portion having spaced undersurfaces adapted toengage spaced portions of a pallet, ribs integral with the body portionand separated by said undersurfaces, said ribs projecting away from thebody portion perpendicularly to the plane of the undersurfaces for adistance substantially equal to the depth of the body portion to disposethe ribs sufficiently away from the top surface of the bar whereby theribs are maintained in a cooler and stronger state than the body portionduring sintering operations.

References Cited in the file of this patent UNITED STATES PATENTS1,633,931 Ellis June 28, 1927 1,912,886 Buckley June 6, 1933 2,322,873Moriarty June 29, 1943

